1. Field of the Invention
The present invention relates to an electronic control device mounted on a vehicle such as an automobile and, specifically, to an electronic control device used in a high-temperature environment. More particularly, the invention relates to an electronic control device which favorably radiates heat generated by a control circuit board and a power module even in a high-temperature environment such as in an engine compartment.
2. Description of the Related Art
A plurality of electronic control devices have heretofore been mounted as a single unit on a vehicle such as an automobile to individually control the installed devices such as engine and the like. Each electronic control device comprises a control circuit unit including a microcomputer which executes logical control operations based upon the electronic data detected by the sensors, and a drive circuit unit which controls an electric power supply to external units such as actuators that drive the objects to be controlled relying upon the results an operation.
Japanese Unexamined Patent Publication (Kokai) No. 2000-323848 discloses an electronic control device that has been used. In this electronic control device, a major portion working as the electronic control device 1 is accommodated in a connector-integrated resin casing 2 with which a connector casing is integrally molded. A data-receiving connector and a power supply connector are disposed by being grouped into one on the side surface of the connector-integrated resin casing 2. This enables the electric connection between the electronic control device and the external electronic part to be accomplished from one side of the unit.
In the electronic control device of this constitution, the connector-integrated resin casing assumes a complex structure which is difficult to mold and assemble. In particular, as the connectors become large and the number of storage units increases, it becomes difficult to arrange the connectors on the same side surface of the connector-integrated resin casing 2. Such an electronic control unit effects the electric connection to an external unit via a wire harness. However, if the connectors are not mounted on the same side surface, it becomes difficult to lay the harness which requires an increased space for mounting. Besides, the cost of production is driven up due to the use of water-proof packings between the resin casing and the closure, and between the resin casing and the heat sink.
Further, Japanese Unexamined Patent Publication (Kokai) No. 7-297561 discloses a prior art related to an electronic equipment housing in which a control circuit unit, a drive circuit unit and a power circuit unit are formed in separate spaces. The power circuit unit is provided with heat-radiating fins to prevent a rise in the temperature in the housing of the electronic equipment. In the drive circuit unit and the power circuit unit, the circuit constituent elements that produce and receive signals are arranged at positions close to each other so as to accomplish a direct electric connection. Here, the electric connection between the drive circuit unit and the control circuit unit is accomplished by using a set of connectors, and the control circuit unit is combined with the power circuit unit that includes the drive circuit unit.
According to the electronic equipment housing of the constitution disclosed in Japanese Unexamined Patent Publication (Kokai) No. 7-297561, the control circuit portion, drive circuit unit and power circuit unit are connected by using connectors. Therefore, parts of the circuit units must be electrically connected to the connectors, and a large amount of wiring must be laid between the circuit units.
Therefore, the above Japanese Unexamined Patent Publication (Kokai) No. 2000-323848 discloses the structure of a combination of an electronic control device that is so improved as can be easily assembled as an electronic equipment. In this electronic control device, the control circuit unit and the power circuit unit are separated from each other. In the control circuit unit, a control circuit substrate is formed being mounted in the control connector-integrated casing with which a data-receiving connector is integrally molded. In the power circuit unit, a heat sink mounting the power control element is mounted on the lower surface of the power supply connector-integrated casing with which a power supply connector is integrally molded. An intermediate layer having relay connection terminals is arranged between the control circuit unit and the power circuit unit, and the connection terminals of the control circuit unit are electrically connected to the connection terminals of the power circuit unit through the relay connection terminals.
In the above electronic control device, the data-receiving connector-integrated casing, power supply connector-integrated casing and heat sink are stacked and adhered to each other and, besides, a closure is mounted on the uppermost portion thereof. Therefore, the electronic control device, as a whole, assumes a three-stage-overlapped constitution.
In the electronic equipment equipped with the power part as described above, the power control element itself generates heat. Therefore, a heat-radiating measure is necessarily taken so that the electronic part will not be damaged by heat. The above electronic control device is equipped with a heat sink to radiate heat generated by the power control element.
The electronic control devices used for a vehicle for controlling the operations of the engines and the like are usually mounted in the engine compartment of the vehicle or are integrally mounted on the actuator. The place of mounting is in a high-temperature environment which is severe. In order to maintain reliability in such an environment, a heat-resistant ceramic substrate is used for forming electronic circuitry for the electronic control.
The ceramic substrate is produced being fired at a high temperature. The size of the work cannot be increased. Therefore, the cost of production becomes high. In order not to use the ceramic substrate, therefore, it becomes necessary to produce a substrate made of a heat-resistant resin of a low cost which can be used in a high-temperature environment to lower the cost of the electronic control unit.
It is, further, a modern trend to so design the automobile as to expand the passenger compartment as much as possible to offer only a very limited space for the engine room. If it is attempted to mount an electronic control unit in such a limited space, consideration must be given to radiating the heat from the electronic parts inclusive of the power control element so as to be used in a high-temperature environment. Besides, since only limited space is available for installing electronic equipment, there is no means to realize the electronic control unit itself in a small size.
In the above-mentioned electronic control device, the fins of the heat sink are lengthened to enhance the heat-radiating efficiency of the electronic parts. This, however, results in an increase in the size of the unit which is against the requirement for decreasing the size. The conventional electronic control device has a connector-integrated casing of a large thickness and, further, requires a heat sink. The electronic control device is too bulky to be mounted in a narrow space such as in an engine compartment.
In order to decrease the size of the electronic control device, therefore, a contrivance is necessary for decreasing the thickness of the connector-integrated casing. Here, if it is attempted not to use the heat sink which is a cause of making the device bulky, it becomes necessary to further increase the heat-radiating efficiency for the electronic parts in a high-temperature environment. Besides, the electronic control device mounted on a vehicle such as an automobile must be so constituted as will not to be detached or as will not to develop defect in the connection despite of receiving vibration while the vehicle is traveling.
It is therefore an object of the present invention to provide an electronic control device which is small in size, efficiently radiates heat and is easily installed even in a narrow space in high-temperature conditions in an engine compartment.